Marc authored Mar 28, 2018 and Brad King committed Mar 29, 2018

This can be used for example to organize all following targets into one
Visual Studio folder:

  set(CMAKE_FOLDER Libraries)
  add_subdirectory(libA)
  add_subdirectory(libB)
  set(CMAKE_FOLDER Executables)
  add_subdirectory(progA)

Another possibility is using the current directory name for all
following targets in subdirectories:

  get_filename_component(dirname "${CMAKE_CURRENT_SOURCE_DIR}" NAME)
  string(APPEND CMAKE_FOLDER "/${dirname}")